Contrast-Enhanced Ultrasound Combined With Biopsy for the Preoperative Diagnosis of a Rare Pelvic Schwannoma: A Case Report.

BACKGROUND Primary pelvic schwannomas are rare and often misdiagnosed due to non-specific imaging features. Accurate preoperative evaluation remains a challenge. The clinical utility of contrast-enhanced ultrasound (CEUS) combined with time-intensity curve (TIC) analysis and targeted biopsy was evaluated for the preoperative diagnosis and management of a pelvic schwannoma. CASE REPORT A 66-year-old man presented with dysuria and lumbago. Imaging revealed a large, mixed cystic-solid pelvic mass. Conventional ultrasound demonstrated a predominantly cystic-solid lesion with limited Doppler flow, whereas CEUS showed progressive dendritic enhancement of the viable solid component from the periphery toward the center, with non-enhancement of cystic or necrotic areas. TIC analysis demonstrated a distinctive "equal-in and slow-out" perfusion pattern, supported by quantitative parameters (rise time, time to peak, fall time, and washout area under the curve). Based on these perfusion characteristics, ultrasound-guided biopsy was directed toward hyperenhanced viable regions while avoiding necrotic zones, thereby improving tissue sampling accuracy. Immunohistochemistry confirmed S-100 and SOX-10 positivity, establishing a definitive diagnosis. Complete surgical resection with bladder defect repair was performed. Postoperatively, urinary function recovered, and no recurrent urinary or pelvic symptoms were reported during outpatient follow-up. CONCLUSIONS Quantitative CEUS-TIC analysis combined with targeted biopsy provides an effective preoperative diagnostic strategy for pelvic schwannomas. The observed CEUS-TIC perfusion pattern may correspond to the heterogeneous microvascular distribution of Antoni A and Antoni B regions; however, this hypothesis requires validation in future imaging-pathology correlation studies.